There are many applications wherein it is necessary to house elements in a tightly sealed environment. For example, it is often necessary to house computer systems in cabinets that are capable of shielding the electronic components thereof against electromagnetic interference (EMI). An EMI cabinet for shielding such electronic components must employ an extremely tight sealing arrangement to accomplish its intended objective. It is quite common, particularly in large cabinets, to include a plurality of latches spaced along the door to provide, or insure that the door is tightly sealed against the cabinet housing.
In one prior art cabinet arrangement a vertically oriented actuating handle is pivotally connected to the door, and includes a plurality of vertically spaced-apart latching members that are actuated, in unison, by movement of the handle. Each of the latching members includes a helical groove for engaging with a keeper pin secured to the casing of a housing. When the door is in a closed position, the handle can be actuated to cause the helical groove of each latching member to slide into engagement with its associated keeper pin. Thereafter, continued movement of the latching members causes the helical grooves thereof to move relative to the pins and force the door into a tight, sealing relationship with the cabinet housing.
The above-described latching system has several inherent deficiencies. First, a high frictional force is established between the keeper pins and the walls of the helical grooves as the door is being forced tightly against the housing. This high frictional force tends to excessively wear both the pins and grooves to damage the latching system. Moreover, the orientation of the helical grooves relative to the pins tends to impose an extremely severe lateral force on the pins, which, after repeated opening and closing of the cabinet, can actually bend the pins laterally so that they are no longer functionally cooperable with their associated latching members.
U.S. Pat. No. 2,424,962, issued to Best, discloses a latch mechanism including a lever 24 that is pivotally interconnected intermediate its longitudinal ends through a pivot pin 32. The right end of the lever is employed as the handle to operate the system. Thus, the latching head and handle are part of a single member, and cannot move relative to each other.
U.S. Pat. No. 2,477,472, issued to Wright, relates to a self-locking latch employing a toggle lever 16 disposed between trigger lever, or handle 21, and a hook member 14. This a more complex system than one which does not require a toggle lever between the actuating handle and the latching member.
U.S. Pat. No. 2,732,238, issued to Dornberg, relates to a latching system in which relative movement takes place between a hook 28 and a lever 30 in order to bring the hook into engagement with lateral pin 23 to accomplish the locking operation. The arrangement of elements in this system is quite complex.
U.S. Pat. No. 2,894,777, issued to Hogan, discloses a latching system in which the path of travel of hook 8 is controlled by the dimensions and positions of two links 10 and 13. Moreover, movement of the hook 8 is accomplished through actuation, or movement of handle 21 and yoke lever 19. There are a significant number of links and interconnecting members required in the operation of the Hogan system; rendering it quite complex.
U.S. Pat. No. 3,214,207, issued to Swanson, includes a movable linkage arrangement between an actuating handle (e.g. 27) and a latching member or hook (e.g. 35). The introduction of additional linkage members between an actuating handle and latching member is more complex than a latching system wherein such additional linkage members can be omitted.
U.S. Pat. No. 3,259,411, discloses a system wherein a drawhook is directly connected through a rotatable connection to an actuating handle 26. In this device movement of the handle 26 in a clockwise direction, as viewed in FIG. 3, causes the drawhook 40 to ride along the bolt 18 until the latching action is complete. The drawhook 40 is maintained in engagement with the bolt through the action of a spring 46. Although this latching arrangement is somewhat less complex than several of the latching arrangements described heretofore, there is still a necessity to maintain the drawhook 40 in engagement with the bolt. The necessity of requiring the drawhook 40 to actually ride on the bolt to maintain the desired positional relationship between them is not believed to be the most desirable arrangement for latching systems of the type forming the subject matter of this invention.